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Topic: Hofmann Rearrangement Yields (Read 3630 times)

dingbow

Pupae

Posts: 84

Re: Hofmann Rearrangement Yields

« Reply #100 on: August 29, 2011, 10:03:16 AM »

This stuff doesnt dry very easily and im not going to bother with recrystralisation at this point. I attempted a MP test though of this unpurified substance and its something like 67-72c. It seemed to decompose though, losing some mass and becoming yellow.

After vac filtration the weight was around 40g, after some drying time it came down to 25g, but also taking on a light yellow colour. A day later and its still damp and 25g.

It will used as is in a rearrangement.

Edit: FYI, 2.83g of CYA was filtered, a bit above the molar equivalent of TCCA that went in. The extra weight could possibly be some N-Chloroamide that had precipitated, I dont know - the CYA was dried to a crisp so I dont think it was moisture.

« Last Edit: August 29, 2011, 10:05:31 AM by dingbow »

reDEEMed

Subordinate Wasp

Posts: 202

Re: Hofmann Rearrangement Yields

-Fully dissolved 10g amide into 100ml MeOH (took tiny bit of heat to speed things up)-Added 4.1g TCCA, stirred for an hour (some evolution of heat occurred)-Solid precipitate formed fairly quickly after addition of TCCA, assuming this precipitate is CYA-CYA filtered-Instead of boiling off solvent (pita to setup and timely) to obtain N-Chloroamide solid, I precipitated it by addition of H20, seemed to work great.

Few things work mentioning, my TCCA was a solid block that had copper sulfate mixed in. This was removed by powdering the block and stirring in H20, which dissolved the copper sulfate, then filtered and dried it as much as I could be bothered. MeOH was not dried. The final product obtained is a very clean white powder with no smell what so ever. Currently drying, so when thats done I will post yield.

I'll get a MP test for this substance too. Im pretty excited to see how this stuff goes in the rearrangement.

Wow, I wonder why mine came out so gooey? If you're not drying your methanol either, I don't get that. Doesn't seem to matter to the rest of the rearrangement, though.

I can't tell you how many times I've run this reaction at this point, a lot! With stacks upon stacks of printed out patents and notes feverishly scribbled here and there. But the other day, having had enough and intrigued by the results blahblahblah's monkey got, I just said fuck it. I threw away every single note I had and I dumped in 40gms of amide. Having seen the changes in character this solution normally undergoes, I just watched it with no plan on what to do. I just played it by ear the entire way. I had a good feeling about it. Well, my first wash yielded 15gms of damn fine amine, with two more washes giving me another almost 10gms. It's only a matter of time before this rxn is my bitch.

"Ego is a structure that is erected by a neurotic individual who is a member of a neurotic culture against the facts of the matter. And culture, which we put on like an overcoat, is the collectivized consensus about what sort of neurotic behaviors are acceptable."— Terence McKenna

fries

Larvae

Posts: 26

Re: Hofmann Rearrangement Yields

« Reply #102 on: August 30, 2011, 08:29:36 AM »

25g of amine from 40g amide sounds spectacular... Would you mind writing down/giving some of the details of the process you used?

dingbow

Re: Hofmann Rearrangement Yields

Wow, I wonder why mine came out so gooey? If you're not drying your methanol either, I don't get that. Doesn't seem to matter to the rest of the rearrangement, though.

Did you boil off your MeOH to obtain gooey chloroamide? Did you then have success with this in the rearrangement? How did you rearrange it?

I ask because im having trouble rearranging what I thought was the chloroamide. It went the usual milky white (albeit with more heat then usually required and longer time), so some form of reaction occurred, leaving a non water soluble crystaline powder in the reaction, that will not further convert to the amine.

I simply added the supposed N-Chloroamide to a solution of NaOH that was then heated.. so far I dont have amine though and its not looking good.

Formation of the o-methyl carbamate is affected by TCCA in methanol in good yields. Obviously FMOC can be cleaved to yield the amine in acid. Is acid catalyzed hydrolysis of the methyl carbamate an option?

edit: also, is anyone neutralizing their oxidant before performing the rearrangement? residual oxidant seems like a real yield killer to me...

Im a bit confused here, the attached reference from Redeemed says that the product of amide + TCCA in MeOH = N-Chloroamide, though these quotes mention chloroamines and carbamates.

« Last Edit: August 30, 2011, 11:33:11 AM by dingbow »

akcom

Dominant Queen

Posts: 430

Re: Hofmann Rearrangement Yields

« Reply #104 on: August 30, 2011, 05:32:32 PM »

The o-methyl carbamate is obtained only in the presence of strong base (sodium methoxide usually)

Re: Hofmann Rearrangement Yields

Wow, I wonder why mine came out so gooey? If you're not drying your methanol either, I don't get that. Doesn't seem to matter to the rest of the rearrangement, though.

Did you boil off your MeOH to obtain gooey chloroamide? Did you then have success with this in the rearrangement? How did you rearrange it?

I ask because im having trouble rearranging what I thought was the chloroamide. It went the usual milky white (albeit with more heat then usually required and longer time), so some form of reaction occurred, leaving a non water soluble crystaline powder in the reaction, that will not further convert to the amine.

I simply added the supposed N-Chloroamide to a solution of NaOH that was then heated.. so far I dont have amine though and its not looking good.

As funny as it is to you guys, the Hoffman as a whole did not produce shit for me several times. Now, looking back, I'm almost positive that it was my workup that was flawed. The very first time I had any success was when I used the TCICA first then rearranged the goo. That was the very first time I got bitter crystal. All I did was mix it with a minimum of water and dripped it in to 70C NaOH solution with stirring. IIRC I let it still for an hour or so. But, after the other day I wont bother with it again unless that can push yields toward quantitive.

Fries- I didn't write anything down or take any kind of notes. I came to conclusion that was not helping as yields were not getting any better. I just took what I knew from watching this reaction forty billion times and I watched it, with no heat to see how it would change. I already knew that the brown precipitate was my amine it just wasn't ready so to speak. One day I took the time with a flask of water and wrote out the temps on my hotplate, this has proven to be the most worthwhile thing I've done lol. Now I can wind off my dial to 50C or whatever and walk off and if I come back in an hour, it's 50C, not 48 not 52, 50! So I just started gently adding heat once the reaction had peaked at room temp and I was convinced that was all it was gonna do. I nudged on the heat to 50 and let it sit for a few hours, sure enough it pushed more of my shit back out of solution and into that brown precipitate. I did this again and again until I was at 65, not going past there. Actually I did bump it up to 70 briefly but no change seemed apparent in color, so I bumped back down. I can't say exactly how long I let it go, all day, not including the night in the fridge in the ice bath. After I was done heating I just let it cool on the hotplate to room temp. Once the hotplate was cool enough I turned stirring off which immediately caused buckets of that red oil to drop out of suspension.

This is just the beginning I really have the feeling I can get into the steady 70's or even 80's on yield. You already know what you want to see, throw those fucking notes away and make it show you what you want to see!!

"Ego is a structure that is erected by a neurotic individual who is a member of a neurotic culture against the facts of the matter. And culture, which we put on like an overcoat, is the collectivized consensus about what sort of neurotic behaviors are acceptable."— Terence McKenna

fries

Larvae

Posts: 26

Re: Hofmann Rearrangement Yields

Fries- I didn't write anything down or take any kind of notes. I came to conclusion that was not helping as yields were not getting any better. I just took what I knew from watching this reaction forty billion times and I watched it, with no heat to see how it would change. I already knew that the brown precipitate was my amine it just wasn't ready so to speak. One day I took the time with a flask of water and wrote out the temps on my hotplate, this has proven to be the most worthwhile thing I've done lol. Now I can wind off my dial to 50C or whatever and walk off and if I come back in an hour, it's 50C, not 48 not 52, 50! So I just started gently adding heat once the reaction had peaked at room temp and I was convinced that was all it was gonna do. I nudged on the heat to 50 and let it sit for a few hours, sure enough it pushed more of my shit back out of solution and into that brown precipitate. I did this again and again until I was at 65, not going past there. Actually I did bump it up to 70 briefly but no change seemed apparent in color, so I bumped back down. I can't say exactly how long I let it go, all day, not including the night in the fridge in the ice bath. After I was done heating I just let it cool on the hotplate to room temp. Once the hotplate was cool enough I turned stirring off which immediately caused buckets of that red oil to drop out of suspension.

This is just the beginning I really have the feeling I can get into the steady 70's or even 80's on yield. You already know what you want to see, throw those fucking notes away and make it show you what you want to see!!

So, just to get this strate... The above description was with the original household bleach and NaOH hoffman? It's not always clear in your posts when you're talking about TCCA or bleach.

"once the reaction had peaked at room temp" What do you mean by this - When it starts going brown? Or once everything has turned into oil? In my mind the raction has peaked once everything has turned into oil (like in my pictures a few posts ago). By this stage i'm not sure if there is anything left in my reaction to bother with heating. I once tried heating the reaction after it had reached this stage and it didn't give any better yield than the runs with no heating.

I'm wondering if your gradual or long period of heating have something to do with this working so well for you. Has anyone else seen this reaction been done at these temps over such a long period of time?

reDEEMed

Subordinate Wasp

Posts: 202

Re: Hofmann Rearrangement Yields

« Reply #107 on: August 31, 2011, 01:17:17 AM »

That was with straight bleach. I added a little extra to make sure there was enough (like 20mls). When I say peaked, I simply mean that it had obviously plateaued, nothing more was going to happen. So at this point I nudge it forward with a little heat and continue to do this nudge wait for things stabilize nudge some more. I probably could have went further with this batch, but it was so obvious that I had a boatload of oil the excitement was killing me, so I ended it. All I know for sure is that for me, over analyzing was keeping me from seeing the obvious. I quite literally just watched the shit and then reacted to the visual cues the way my gut told me too. Just try it. Dump 40gms of amide in minimum and toss your notes. I think also there is definitely something to bigger batch size and how it relates to bigger percent yields.

"Ego is a structure that is erected by a neurotic individual who is a member of a neurotic culture against the facts of the matter. And culture, which we put on like an overcoat, is the collectivized consensus about what sort of neurotic behaviors are acceptable."— Terence McKenna

dingbow

Pupae

Posts: 84

Re: Hofmann Rearrangement Yields

The o-methyl carbamate is obtained only in the presence of strong base (sodium methoxide usually)

Yeah thats what I thought. I wonder if the dampness of my chloroamide was a problem as it would have contained some MeOH (it weighed more then twice what it should have). Could the MeOH have reacted with the NaOH solution to create the carbamate?

I'll try TCCA again, 2 slightly different methods. Once the chloroamide is formed, i'll halve it, evaporate the MeOH off one half like Redeemed did and precipitate out the other half with water like I did the last time. On the latter approach i'll wash the end product with water more and make sure its dry before the rearrangement.

As funny as it is to you guys, the Hoffman as a whole did not produce shit for me several times. Now, looking back, I'm almost positive that it was my workup that was flawed. The very first time I had any success was when I used the TCICA first then rearranged the goo. That was the very first time I got bitter crystal. All I did was mix it with a minimum of water and dripped it in to 70C NaOH solution with stirring. IIRC I let it still for an hour or so. But, after the other day I wont bother with it again unless that can push yields toward quantitive.

Probably, the first few failures on the hofmann I had were work up related. The biggest help, especially with regard to yield was a post on PS where someone noted to extract the amine out of the hofmann whilst it was still warm, around 60c, whilst the amine had not yet gotten trapped into the solidified mass at the bottom.

Did you end up getting a yield figure on TCCA from amide to amine? Oh and was your chloroamide water soluble?

reDEEMed

Subordinate Wasp

Posts: 202

Re: Hofmann Rearrangement Yields

« Reply #109 on: August 31, 2011, 05:26:18 PM »

No, I didn't give up. I just had to do something quick and I knew the bleach worked predictably so I used it. I will still be playing around, I just had some time constraints that made experimentation not feasible.

Java is the one who first mentioned extracting from 60C solution. If you're gonna copy anyone he's the one to copy. Dude is ridiculously on top of shit.

"Ego is a structure that is erected by a neurotic individual who is a member of a neurotic culture against the facts of the matter. And culture, which we put on like an overcoat, is the collectivized consensus about what sort of neurotic behaviors are acceptable."— Terence McKenna

jon

Foundress Queen

Posts: 1,883

Re: Hofmann Rearrangement Yields

« Reply #110 on: September 01, 2011, 09:45:41 AM »

also mda is volitile with steam you should hve luck with steam distillation to remove it from the heavy tars

fries

Larvae

Posts: 26

Re: Hofmann Rearrangement Yields

All I did was mix it with a minimum of water and dripped it in to 70C NaOH solution with stirring. IIRC I let it still for an hour or so. But, after the other day I wont bother with it again unless that can push yields toward quantitive.

If this is correct (I have no idea, haven't read anything about it as I've not been interested in this route) then it wouldn't be chloroamide precipitating out when you add water.

« Last Edit: September 01, 2011, 12:56:06 PM by fries »

letters

Subordinate Wasp

Posts: 138

Re: Hofmann Rearrangement Yields

« Reply #112 on: September 01, 2011, 04:36:12 PM »

not sure which chloramide you guys are speaking of, but if it is the one derived from that aldehyde mentioned by twodogs, then it is not water soluble, at least not to any appreciable extent. it is however soluble in methanol, as well as various ethers.

reDEEMed

Subordinate Wasp

Posts: 202

Re: Hofmann Rearrangement Yields

« Reply #113 on: September 01, 2011, 05:01:21 PM »

Ya know what, it was dissolved in methanol, not water. My bad.

"Ego is a structure that is erected by a neurotic individual who is a member of a neurotic culture against the facts of the matter. And culture, which we put on like an overcoat, is the collectivized consensus about what sort of neurotic behaviors are acceptable."— Terence McKenna

dingbow

Pupae

Posts: 84

Re: Hofmann Rearrangement Yields

« Reply #114 on: September 02, 2011, 05:10:42 AM »

oh you dissolved your chloroamide into MeOH and dripped that into the hofmann?? Interesting... alcohol was something I had considered as a co-solvent in the hofmann but didnt try it because it seemed it would react with the NaOCl. Though if you have the chloroamide, your past that stage, interesting!

Yeah I assumed the chloroamide was not water soluble, because the literature stated recrystalisation from benzene.

reDEEMed

Subordinate Wasp

Posts: 202

Re: Hofmann Rearrangement Yields

« Reply #115 on: September 02, 2011, 06:24:26 AM »

I did it because it was already gooey and it was gooey because of something that happened in methanol lol. Flimsy logic, but that's all I got to work with.

"Ego is a structure that is erected by a neurotic individual who is a member of a neurotic culture against the facts of the matter. And culture, which we put on like an overcoat, is the collectivized consensus about what sort of neurotic behaviors are acceptable."— Terence McKenna

letters

Subordinate Wasp

Posts: 138

Re: Hofmann Rearrangement Yields

« Reply #116 on: September 02, 2011, 06:53:13 AM »

reacting the chloramide with methanol and naoh will yield a mixture of the methyl carbamate, primary amine and maybe some urea as well. the chloramide you speak of does not react with methanol under neutral conditions. there is no reason to get "gooey" chloramide, it is a solid, fully crystallizable.and "Ya know what, it was dissolved in methanol, not water. My bad." is something i can not accept. the rhodium/barium style intended mistakes is something i really frown upon. if this was an honest mistake, ok. but ill be around watching, and will jump in whenever i see bullshit being written.

reDEEMed

Subordinate Wasp

Posts: 202

Re: Hofmann Rearrangement Yields

« Reply #117 on: September 02, 2011, 04:59:57 PM »

It was an honest mistake, I tossed my notebook, the whole thing and that procedure is not something that's been on my mind lately. You don't have to worry about me writing 'bullshit' in this thread anymore because I'm done with it. My yields are now very very acceptable and I've said all I can say as to why that is.

I really have nothing more to add here.

"Ego is a structure that is erected by a neurotic individual who is a member of a neurotic culture against the facts of the matter. And culture, which we put on like an overcoat, is the collectivized consensus about what sort of neurotic behaviors are acceptable."— Terence McKenna

dingbow

Pupae

Posts: 84

Re: Hofmann Rearrangement Yields

reacting the chloramide with methanol and naoh will yield a mixture of the methyl carbamate, primary amine and maybe some urea as well. the chloramide you speak of does not react with methanol under neutral conditions. there is no reason to get "gooey" chloramide, it is a solid, fully crystallizable....rhodium/barium style intended mistakes...

Right ok, so then the question is what ratios of carbamate, amine and urea do you get and if the major component is the amine, are the yields satisfactory.

dingbow

Pupae

Posts: 84

Re: Hofmann Rearrangement Yields

« Reply #119 on: September 08, 2011, 07:54:28 AM »

So heres what I have done thus far;-took a small amount of chloroamide saturated MeOH and tried to evaporate it.. decomposition seemed to occur so gave up on that.-Took half of remaining saturated MeOH solution and ran it through rearrangement as is (Redeemed method), which resulted in the same as my first run, a white crystraline precipate that would not convert to amine. Not so surprising.

There seemed to be a fishy amine smell from the reaction though, so I proceeded to extract 2x from the reaction solution after filtering off the solids. The non polar extracts were then washed with dilute HCl solution, the washes evaporated to yield a TINY amount of amine.

This is somewhat encouraging, it shows the reaction can indeed produce the amine and hopefully can be tweeked to yield amine as the major component. From my reading, apparently the isocyanate can be trapped by the MeOH and convert to the carbamate, which could be my problem (especially given the weight of the chloroamide was double what should have been there @ 100% yield).

So, I have now recrystalised some chloroamide with xylene, which was obtained by precipitating it out of the MeOH with water, in the hope that its removed any last trace of MeOH. Its dry now and I will attempt a rearrangement on it soon.

Actually I might recrystalise more chloroamide and see if it loses weight post recrystalisation.

PS; I tried doing a MP on the chloroamide again, it melted into this thick clear liquid and upon cooling did not change appearance but hardened. The weight of the product did not change, I reheated again and it went white, again not losing any weight but going by appearance it seems to be a different compound.